Overload protective device



Feb. 26, 1924. 1,485,157

C. J. AXTELL QVERLOAD PRoimcTIvE DEVICE Filed July 9, 1920 Invehtor: YClinton J. Axtell 9%? Hjs Attorney.

Patented Feb. 26, 1924.

UNITED STATES 1,485,157 PATENT OFFICE.

CLINTON J. AXTELL, 0F SCHENECTADY, NEW YORK, ASSIGNQR T0 GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

OVERLOAD PROTECTIVE DEVICE.

Application filed July 9,

To all whom it may concern:

Be it known that I, CLINTON J. AXTELL, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Overload ProtectiveDevices, of which the following is a specification. 7

My invention relates to protective devices for electric circuits wherebyan excessive current will insure an opening of the circuit to preventinjury to translating devices connected thereto. More specifically, myinvention relates to an overload circuit breaker adapted to operate atany one of a plurality of different values of current, and the inventionis particularly useful for operation on a circuit in which the potentialof the current differs from time to time. A familiar instance of thiskind is an electric railway on which the cars operate at 600 volts onsome parts of the line and at 1200 volts on the other parts. In such anequipment, if the cars are provided with four motors, they are connectedin parallel when running at full speed on the 600 volt section of theroad, and connected in series parallel (two parallel groups of two inseries) when the cars are operating on the 1200 volt section of theline. In such an arrangement, the current taken from the 600 voltsection will be approximately double that taken from the 1200 voltsection for the same speed of operation.

The object of my invention is to provide a circuit breaker which willaccommodate itself to the change from operation upon one voltage tooperation upon another with the corresponding change in current, andwill protect the motors equally well under both conditions.

In carrying my invention into effect, I provide a circuit breaker havingan operating electromagnet with a series coil enerized in accordancewith the current taken rom the source of supply, and vary the pull ofthe electromagnet in accordance with the voltage of the supplyse'ctionby varying the magnetic reluctance of the operating electromagnet. Oneembodiment of my invention comprises an operating electromagnet having aseries coil and a movable member which is electromagnetically operatedto vary the magnetic reluctance of the operating electromagnet andthereby automatically 1920. Serial No. 394,983.

vary the setting at which the overload protective device will disconnectthe translating devices from the source of supply. Provision is thusautomatically made for accom modating the protective device to thedifferent value of current or the setting of the protective device inaccordance with the voltage of the supply circuit.

For a better understanding of my invention, reference is had to theaccompanying drawing wherein I have shown an embodiment of my inventionfor purposes of illustration. Referring to the drawing, the translatingdevices to be protected, in this case the series wound motors 10, 11, 12and 13, are adapted to be connected to the source of supply through theoperation of the master controller 14 by the closing of theelectromagnetic line switch '15. This electromagnetic line switch orcontactor 15 is controlled by my improved circuit breaker or overloadprotective device 16 having a series coil 17 energized responsively tothe motor current and a magnetic structure having a movable member orplunger 18 for varying the reluctance of the magnetic circuit inaccordance with the value of current at which the overload protectivedevice is to operate. The protective device is also provided with aswitch member 19 having contacts in the coil circuit of the linecontactor 15. An electromagnet 20, having a shunt coil 21 and a movableplunger 22 mechanically connected with the plunger 18, is adapted to beenergized when the motors are connected to the source of supply forparallel operation by throwing the series parallel switch 23 to itslower position. The series parallel switch is shown in the drawing asbeing thrown in its upper position at which the motors are connected inseries parallel across the supply circuit. When the series parallelswitch is thrown to its lower position to connect the motors in multiplethe movable contact 24 makes engagement with the stationary contacts 25and thereby connects the shunt coil 21 across the supply circuit. Whenthe overload protective device responds in accordance with thepredetermined value of cur-- rent, the switch member 19 is locked in theopen position by means of the biased pivoted detent or catch 26. Thisdetent 26 may be released by the energization of the electromagnet 27when the pilot switch 28 is closed, thereby attracting the detent 26 andperer voltage section of the line. For purposes of explanation, it willbe assumed that the higher voltage is 1200 volts. The motors will beaccelerated up to ll operating speed by continuing the movement of themaster switch 1 which thereby etfects the cutting out of the startingresistor 31 section by section in a well understood manner. Theelectromagnetic switches tor cutting out the starting resistor and theconnections for the same have not been shown, since this an rangement iswell understood by those skilled in the art. In case an excessivecurrent. is taken from the source of supply, the series coil 17 will beenergized at such a value that. the switch member 19 will open itscontacts and thereby decuergize the winding circuit of the linecontactor 15, thereby disconnecting the motors from the trolley wire 32(the source of supply). The detent 26 will prevent the switch member 10from reclosing its contacts and the operator will then return the masterswitch 1% to its oif position, thereby reinserting the starting resistor31 in the motor circuit. In order to reconnect the motors to the supplycircuit, the pilot switch 28 is closed, thereby energizing theelectromagnet 27 and attracting the pivoted detent 26. .Vhen the switchmember 10 has closed its contacts, the pilot switch 28 may be reopenedso as to render the detent 2G etlective to lock the switch member 19 inthe open position in response to the occurrence another overload. lV henthe series paralleling switch 23 is thrown to its lower position, atwhich its upper contacts make engagement with the stationary motorterminal contacts, the motors will be connected in parallel across the 51 circuit, and the shunt winding 21 will be energized through thecontact 2 1:. This will cause the plunger 22 to be drawn upward withinthe shunt coil 21 and the. plunger 18 to be also moved upwardly, therebyincreasing the magnetic reluctance of the magnetic structure or theoverload protective device 10. This will change the setting of theoverload protective device to accommodate it to the change in potentialof the supply circuit, and the overload protective device will not tripopen until the current in the series coil 17 is substantially doublethat at which the protective device previously open ated when the motorswere operating on the 1200 volt section of the line. bviously, theprotective device may be adjusted or set to operate at any desired valueof current when operating on the 1200 or (500 volt section of line byvarying the position oi? the plunger it}. in order to simplify thedrawing, no means has been shown for holding the plunger in its lowerposition since the provision of such means obvious and those skilled inthe art will readily supply the same.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof;but I desire to have it understood that the apparatus shown is onlyillustrative, and that the invention can be carried out by any othermeans.

hat I claim as new, and desire to secure by Letters Patent 01. theUnited States, is

1. An overload circuit breaker adapted to open at a plurality ofpredetermined different values of current in the circuit controlledthereby, comprising a coil energized responsivcly to the current in thecontrolled circuit, a magnet structure therefor, a switch ieinbercontrolled thereby for controlling the controlled circuit andelectromagnetic m ans for changing the magnetic reluctance ot the saidmagnetic structure to change the value of current at which the circuitbreaker is to open.

2. An overload circuit breaker adapted to open at a plurality ofpredetermined different values of current in the circuit controlledthereby, comprising an operating electromagnet having a coil energizedresponsively to the current in the controlled circuit, a switch membercontrolled thereby for controlling the controlled circuit. andelectromagnetic means for varying the pull of the operatingelectromagnet to change the value of current at which the circuitbreaker is to open.

3. An overload circuit breaker adapted to open at either of twodifferent values of current in the circuit controlled thereby,comprising an electrom'agnet having a coil energized responsively to thecurrent in the controlled circuit, a magnet structure there- "for havinga movable member for varying the magnetic reluctance of the structure, aswitch member controlled by the electromagnet for controlling thecontrolled circuit, electromagnetic means for varying the position ofthe said movable member, and means for controlling the saidelectromagnetic means to vary the value of current at which the circuitbreaker is to open.

4. An overload circuit breaker adapted to open at one value of currentwhen the translating device controlled by the circuit breaker isconnected to a source of supply of one voltage and to open at a hi hervalue of current when the translating evice is con nected to a source ofsupply of lower voltage, comprising a coil energized by the our rent inthe circuit of the translating device, a magnet structure therefor, aswitch member controlled thereby for controlling the circuit of thetranslating device, and electromagnetic means energized from the sourceof supply of lower potential for increasing the magnetic reluctance ofthe said magnetic structure to increase the value of current necessaryto open the circuit breaker.

5. An overload circuit breaker adapted to open at one value of currentwhen the translating device controlled by the breaker is connected to asource of supply of one voltage and to open at a higher value of currentwhen the translating device is connected to a source of supply of lowervoltage, comprising a coil energized by the current, a magnet structuretherefor, a switch member controlled thereby, the said magnet structurehaving a magnetic movable member, and an electromagnet energized fromthe source of lower potential for moving the said movable member to varythe magnetic reluctance of the said magnet structure to vary the valueof current at which the circuit breaker is to open.

In witness whereof, I have hereunto set my hand this 8th day of July,1920.

CLINTON J. AXTELL.

